SGS-LTER Long-term Monitoring Project: Carnivore Scat Count on the Central Plains Experimental Range, Nunn, Colorado, USA 1997 -

Carnivores are among the most conspicuous, charismatic and economically important mammals in shortgrass steppe, yet relatively is little is known about their populations or of the ecological factors that determine their distribution and abundance, in part because densities tend to be low. Mammalian carnivores represent the top predators in grassland food webs, consuming rodents, rabbits, young ungulates and other small vertebrates. In addition, shortgrass steppe is the primary habitat of the swift fox (Vulpes velox), a species of special conservation concern throughout most of its range. Fox populations are thought to be limited by predation from coyotes (Canis latrans), the most common carnivore in these grasslands and a species of interest, both for its ecological roles and well as a target species for human exploitation, ie hunting and predator control. In 1994, we implemented a low-intensity sampling scheme to monitor long-term changes in relative abundance of mammalian carnivores and help us examine interactions between these predators and their small mammal prey, including rodents and rabbits. We estimated relative abundance of carnivores using scat surveys along a fixed route. Four times each year (January, April, July, October), we drove a 32-km route consisting of pasture two-track and gravel roads on the CPER. We first drove the route to remove all scats (‘PRE-census’); we then returned ~14 d later and counted the number of scats deposited on the route (‘CENSUS’). We recorded the species that deposited the scat and estimated the scat age based on external appearance (4 categories). Beginning in 1997, we recorded the vegetation (habitat) type and topographic position of all scat locations to describe habitat use. Latrines are indicated by locations containing multiple scats. We used the ‘CENSUS’ data to calculate a scat index, defined as the number of scats deposited per km of road per night. The scat index can be used to estimate population density using equations for coyotes (Knowlton 1982) and swift foxes (Schauster et al. 2002) that described the rate of scat deposition from surveys where density was known. To estimate density and compare trends among seasons and years, we omitted scats collected along the 8.3 km of the route that occurred on gravel county roads. These roads are graded sporadically, sometimes between pre-census and census surveys, which tended to remove scats. (NOTE: these observations are NOT omitted in the dataset).食肉目动物是短草草原（shortgrass steppe）中最引人注目、极具魅力且兼具重要经济价值的哺乳动物类群之一，但目前学界对其种群规模以及决定其分布与种群丰度的生态因子所知甚少，部分原因在于其种群密度普遍较低。哺乳纲食肉动物是草原食物网中的顶级捕食者，以啮齿类、兔类、幼有蹄类及其他小型脊椎动物为食。此外，短草草原（shortgrass steppe）是草原狐（Vulpes velox）的核心栖息地，该物种在其分布区内的绝大多数区域均被列为重点保护对象。学界普遍认为，草原狐的种群数量受到郊狼（Canis latrans）捕食的制约；郊狼是该草原中最常见的食肉动物，其不仅因独特的生态功能受到广泛关注，同时也是人类猎捕与天敌防控的目标物种。 1994年，我们启动了一项低强度采样计划，以长期监测哺乳纲食肉动物的相对丰度变化，并助力探究这些捕食者与啮齿类、兔类等小型哺乳类猎物之间的种间互作关系。我们通过沿固定路线开展的粪便调查（scat surveys）来估算食肉动物的相对丰度：每年开展四次调查（1月、4月、7月、10月），沿CPER区域内一条总长32公里的路线行进，该路线由牧场双轨道与碎石公路组成。我们首先沿该路线行进以清除所有现存粪便，即预普查（PRE-census）阶段；约14天后返回，统计该路线上新遗留的粪便数量，即普查（CENSUS）阶段。我们记录了遗留粪便的物种来源，并根据外观特征估算粪便的沉积时长（共分为4个等级）。自1997年起，我们记录所有粪便发现点的植被（生境）类型与地形位置，以分析食肉动物的生境利用模式。粪便堆积点指存在多枚粪便的点位。 我们利用“普查（CENSUS）”阶段的数据计算粪便指数（scat index），该指数定义为每公里道路每夜遗留的粪便数量。针对已知种群密度的郊狼（Knowlton 1982）与草原狐（Schauster et al. 2002），已有研究建立了基于调查得到的粪便沉积率推导种群密度的公式，因此可通过粪便指数估算目标种群的密度。为准确估算种群密度并对比不同季节与年份的种群变化趋势，我们剔除了路线中8.3公里县级碎石公路路段上采集的粪便数据：这类道路会不定期进行路面平整作业，有时作业时间恰好处于预普查与普查阶段之间，该操作往往会清除遗留的粪便。（注：本数据集未剔除上述观测数据）